Expression of CCR2 on Monocytes and Macrophages in Chronically Inflamed Skin in Atopic Dermatitis and Psoriasis
Christian Vestergaard , Helle Just , Jane Baumgartner Nielsen , Kristian Thestrup-Pedersen , Mette Deleuran
Monocytes form a significant component of the inflammatory reaction taking place in the skin of atopic dermatitis and psoriasis. Chemokines are pivotalin mediating the attraction of leucocytes to sites of inflammation. The CC-chemokine, monocyte chemotactic protein 1 (MCP-1/CCL2), is expressed by keratinocytes in both atopic dermatitis and psoriasis. MCP-1 binds to the chemokine receptor CCR2 which is known to be expressed on monocytes and macrophages. We examined the expression of CCR2 on peripheral blood monocytes from patients with psoriasis ( n =8) and atopic dermatitis ( n =7)and found it to be expressed on approximately 90% of the cells, whereas monocytes from healthy donors had a significantly lower CCR2 expression( p <0.05). Skin biopsies from patients suffering from atopic dermatitis and psoriasis revealed that CCR2-positive cells expressed CD163, a marker for monocytes/macrophages. However, not all CD163-positive cells expressed CCR2, which could be interpreted as a mechanism for retaining the macrophages in the skin. Furthermore, we found that keratinocytes are able to express MCP-1, when stimulated with tumour necrosis factor-α and/or interferon-γ in a dose-dependent manner. Thus MCP-1 and CCR2 interaction is likely of importance for the monocyte/macrophage trafficking of inflammatory skin disorders.